Variable resistance device



June 14, 1938. N, Q SCHELLENGER 2,120,651

VARIABLE RES I STANCE DEVICE Filed June 1l, 1954 2 Sheets-Sheet l INVE'NTOE.

NEM/Tm U. 5UHELLENGER.

June 14, 1938- N. c. scHELLENGER VARIABLE RESISTANCE DEVICE 2 Sheets-Sheet 2 JN VE N TOE.

Filed June ll, 1954 Patented June 14, 1938 UNITED STATES PATENT oFFlcE VARIABLE RESISTANCE DEVICE Application June 11, 1934, Serial No. 730,039

5 Claims.

This invention relates to variable resistance devices and more particularly to a plurality of variable resistance units connected in a positively secured tandem relationship to constitute a single device for operation by a single actuating means and including a novel structure for coupling a series of alined shafts.

In variable resistance devices connected in tandem relationship as known heretofore, greatdiiiicuity has been experienced in connecting the various units in a positively secured tandem relationship and at the same time insuring a smooth free rotation of the alined shafts of the several units without any tendency toward binding thereof.

l In the manufacture of variable resistance devices aranged in tandem relationship in mass production by the use of comparatively light grade materials and with low cost operations such as by punch press and forming press operations, veryne tolerances between individual units cannot be adhered to. On the other hand,

the various individual units to be connected in tandem must be .very securely and rigidly fixed to each other to prevent any movement of the said units relative to each other. The actuating shafts of the individual units will consequently often be slightly out of alinement with each other, and upon coupling the various mis-aligned shafts for operation by a single actuating member, a binding action of one or more of the shafts in their respective bearings will necessarily result.

I have found that a plurality of variable resistance units can be comtructed of light materials with low cost operations, that the various elements of these units can be assembled in accurately positioned relationship to each other with maximum allowable tolerances and without lowering the precision of operation thereof, that they can be rigidly and fixedly secured to each other with maximum allowable tolerances of the cooperating securing means and alinement of operating shafts and yet insure a free smooth operation of all shafts in their respective bearings .despite considerable mis-alinement of the shafts.

It is therefore, an object of my invention to provide a variable resistance unit in which the various elements thereof are. properly shielded and insulated and in which the said elements may be easily and rapidly assembled in a securely fixed relationship to each other.

It is another object of my invention to provide a plurality of variable resistance units connected rigidly and securely to each otherto form a tandem device and with the operating shafts thereof (ci. aol-4s) coupled to each otner for smooth free rotation despite considerable misalinement between said shafts.

It is another object of my invention to provide a plurality of yvariable resistance units connected r rigidly and securely to each other to form a tandem device, and eachvariable resistance unit having means for electrostatically shielding the same from an adjacent unit, said. shielding means also being adapted to secure said units to each other.

It is stillanother object of my invention to provide a plurality of variable resistance units connected rigidly and securely to each other to form a compact tandem device, each variable 5 resistance unit having means for electrostatically shielding the same from an adjacent unit, said shielding means between adjacent units being offset to-increase the compactness and rigidity of the tandem device and to prevent undesirable electrical contact between elements thereof.

It is a further object of my invention to provide a novel coupling means between adjacent shafts of a plurality of variable resistance units connected securely to each other to form a tandem device.

It is a still further object of my invention to provide a plurality of variable resistance units constructed of light material by low cost manufacturing operations vand having means for rigidly and securely connecting the same to each other to form a tandem device, said units having operating shafts coupled to each other for smooth free rotation in their respective bearings.

' Still further objects and advantages of this 35 invention will become evident by reference to the following detailed description taken in connection with the accompanying illustrations of one specific embodiment thereof.

In the drawings, which for purposes of clarity, 40 illustrate the invention on a considerably larger scale than the actual size of the device,

Fig. 1 is a vertical sectional View of three variable resistance units secured in tandem relationship;

Flg. 2 is a side elevational view of two Variable resistance units secured in tandem relationship;

l Fig. 3 is an exploded perspective view of two variable resistance units composing a tandem device, with the actuating mechanism removed therefrom;

Fig. 4 is an exploded perspective view of the shafts and coupling means for a. tandem device composed of two variable resistance units;

Fig. 5 is an exploded perspective view of the 55 shafts and coupling means shown in Fig. fi, but taken from another angle;

Figs. 6 and 7 are fragmentary sectional views oi a pair of mis-alined shafts and coupling means positioned therein;

Fig. 8 is a vertical section view showing a cover ear and a corresponding offset portion.

Referring to the embodiment of the invention illustrated in the drawings, A, B, and C designate generally three variable resistance units adapted to be connected in tandem as clearly shown in Fig. l.

The variable resistance unit A comprises an actuating shaft i2 journalled in the bearing it of a bushing it and the hearing 32 of a metallic housing 3|. The bushing it isv securely fixed to an insulating base plate 24 and a washer 29. A metallic drive arm i6 is xedly mounted on the shaft I2 adjacent the end of the said shaft which is journalled in bearing 32. A thrust bearing ill is formed in the housing adjacent journal bearing 32, and a thrust washer i8 is positioned between thrust bearing il and the flxedly secured drive arm I6 to take the end thrust of the shaft. The drive arm i6 is rotatably coupled with a contact arm 20 through the intermediary of an insulating plate i9. The base plate 24 is provided with an arcuate resistance element 22 which may be a coating of carbonaceous resistance material applied directly on the base plate 24 or applied to a separate piece of insulating material 2l which in turn is fastened to base plate 24. il contactor 2i is positioned ontheresistanceelement 22 for sliding or wiping engagement therewith. The contactor 2l is connected to the contact arm ,2U ior actuation thereby. Ilhe contact arm ttl is made of a resilient highly conductive material and is provided with a warped or loowed portion ior maintaining an electrical Contact with a collector ring 2t. The collector ring is formed with an extension arm iii which is iirmly connected to the center terminal 2d which terminal is not directly in contact with the resistance element. The other ttvo terminals are connected to the ehm oi the arcuate resistance element 2li and thus causing the current to flou through the unit in 'the iollovving manner: from one 'oi the end ter= minals 2da to the resistance element 32, to the contacter 2li, to the contact arrn iid, to the collector ring (26, to the extension ill, to the center terminal 2t. For a more detailed disclosure of particular variable resistance unit mechanism and the construction and relationship oi'its various parts, reference is made to inl! co-pending application Serial No. 221,728, iiled April 2l, i934.

The metallic housing Si (Fig. 3), alcove referred to consists o a cup-shaped metallic mernher hav- 'ing an end wail illu and a circular side wall tio. The circular side wall lib is formed with a notched section tft to provide clearance for the terminals 2li and 28a, and with two oppositely disposed notched sections di), 3Q (Fig. 2) for cooperation with a pair of spacing and locating lugs du, lill. A plurality of spaced ears entend from the free end of the side wall 3th :for cooperation with the bottom surface of the hase plate 2d to secure said plate 2t in the housing.

`The end wail la is formed with a shallow ottset portion il surrounding the journal bearing 32, for the purpose of providing a thrust hearing il for the washer id. A comparatively deep offset portion 33 is provided at the peripheral margin of the end wall tia as a continuation of the shallow off-set portion di. 'The ofte-set portion ,im is formed to provide a clearance for the teraandeel minals of the next adjacent variable resistance unit B of the tandem unit shown in Fig. l. A plurality pr o-set'portions 35 are formed at spaced intervals on the marginal periphery of the end wall 3io to provide clearance for the bentover ears 33 of the next adjacent variable resistance unit B. The end wall 3|a is also provided vrith a plurality of spaced slots 36 for a purpose as will be hereinafter described.

Ihe housing 3| is spaced from the base plate 24 by means of the strip i5 of insulating material which is positioned against the inner surface of the side wall 3Ib and acts as a spacer between the inner surface of the end wall Sla and the base plate. This strip is provided with notched portions as clearance for the off-set portions 35 and 38.

The variable resistance unit B is similar in construction to 4the unit A, with the exception that it is provided with a metallic grounding plate di closely adjacent the external surface of the base plate 24, and the ears 33 of unit B are bent over against. the grounding plate 4| instead of the base plate 24. The grounding plate 4| is provided with a plurality of ears 44 struck thereirom and which are of a size and location corresponding to the slots 36 in the end wall Sla. The grounding plate is provided with a centrally located upstanding collar 42 which is adapted to function as a journal hearing for a shaft 50 of the device B. A radially notched portion 43 is formed in the grounding plate 4| as clearance for the terminals of the corresponding variable ree sistance unit. Grounding plate 4| is positioned accurately' on the insulating base 24 with respect to angular movement by the ears 4|b on the periphery of the plate, adjacent each side of the notch Ml, projecting up alongside the terminal supporting lobe 24h on hase 24. Each of the rectangular slots 4|a are positioned to receive one of the cover ears 33 so that all of these ears may be of uniform shape and can be formed over against the ground plate in a uniform manner. These slots cooperating with the ears 33 also serve to more accurately and positively position the cover on the base. Unit El is constructed with a short stulo shaft d@ instead oi a projecting actuating shaft as shown in unit il. The stuh shaft is journalled in collar @t at one end thereof and in journal hearing Si. oi" housing iii at the other end thereof, thus eliminating the bushing iii- Due to elimination oi the said shaft hashing, the insulation washer til of unit B is made consideraioly thicker than insulating washer 25 ci unit Variable resistance device C is also provided with a grounding plate il as shown and described in variable resistance unit E, and also has a stub shaft di instead of a projecting actuating shaft. Unit C differs irorn the other two units in that the housng til thereof is not formed with the offf-set portions 3h, Ell, and lout has an annuu lai', odset, flat-hottomed groove@ to provide a thrust hearing ila and a journal hearing 32a for shaft hl.

A. longitudinally extending slot or groove 45 is cut, or otherwise formed, through the end of shaft it which is journalled in journal hearing 32. Stun shaft has a similar slot 46 formed in each end thereof. and stuh shaft 5| also has a similar slot itil `torinesi therein at the end journalled in collar @it of the grounding plate. The slots of adjacent ends oi the various shafts are arranged in alinernent with each other and a coupling ele,n

ment 41 positioned in each cooperative pair of slots.

The coupling element 41 comprises a slightly elongated metallic body member of a somewhat dumb-bell shaped cross-section, the ends 41a of which are concave as is clearly shown in Fig. 5. The coupling member 41 is formed with enlarged top and bottom portions 41c and an intermediate reduced section 41h. The enlarged top and bottom portions are preferably constructed with a somewhat elliptical or arcuate, cross-sectional contour of a diameter or Width substantially equal to the width of the'cooperating slots 48 and 45 as illustrated in Fig. 4. When assembled, the coupling member 41 has one of its enlarged ends 41C- positioned within slot 49 and the other enlarged end 41c within slot 45. The fit between the enlarged ends and their respective slots is sufficiently close that there will be but very slight rotational play or looseness between shafts.

Irl assembling the variable resistance units to each other, the following procedure is preferably observed:

The upper variable resistance unit C is rst completely assembled as shown in Fig. 1 but with the struck out ears 44 extending downwardly. The housing 3|, including insulation strip |5, of unit B is`then positioned with the end wall thereof flatly against the grounding plate 4| of unit C and with the terminals 29, 29a and bent over ears 33 in register respectively with oi-set portions 38 and 35. The struck out ears 44 of the grounding plate 4| will simultaneously register with slots 36 in the end wall of housing 3| These ears 44 are now bent over to secure the unit C rigidly with housing 3|. The stub shaft 50, assembled with its grounding plate 4|, base plate 24, insulating washer`65, collector ring 26, contact arm 20, contactor 2|, insulating plate |9, drive arm' I6 and thrust washer i9, is provided with a coupling member 41 in the upper slot 46 thereofl and is positioned within journal bearing 32 of housing 3|. The upper end of coupling member 41 is simultaneously brought into register with slot 48 of the shaft of unit C and the base plate 24 is brought to bear against insulating strip |5 and with lugs 40 of the base plate registering'with notches 39 of the housing 30. Then the ears 33 of housing 3| are bent over against the grounding plate 4| of unit B. Fig. 8 shows the manner in which the cover ear 33 fits into the off-set portion 35 to permit the units to be ilatly positioned together. 'I'he lugs 40 and notches 39 serve the dual purpose of locating elements and prevent shifting of the base plate 24 relative to housing 3| due to the provision therein of the wide terminal-clearing notch 34.

As many additional B units as desired may be assembled to the tandem device in the same manner as outlined above. The B units are all identical to each other but differ from the C unit in that the end wall of the housing is off-set to clear the terminals of the unit overlying the same and also to provide clearance for the bent over ears of the next adjacent housing. The B units differ from the A" units in that no bushing or projecting shaft is provided therein, and it is furthermore provided with a grounding plate whereas usually none is needed in the A units.

However. in some cases when it is desirable to more completely shield unit A. or provide positioning ears, a grounding plate may be provided (Figs. 2 and 3). When used. ground plate 60 is assembled between washer 29 and base 24 with bushing. |4 extending through hole 64 and with ears 6| alongside the edges of lobe 24h. Locating ears may be formed from the body of the plate to cooperate with holes in the surface on which the control is to be mounted and so prevent rotation of the control relative to its mounting surface. Ears 6| engage the sides of the terminal supporting lobe 24b to maintain the base and grounding plate in fixed angular relationship. There are also slots 62 inthese ears to receive two of the cover ears. As described above, these slots 62 and ears 6| on theA grounding -plate and ears 33 on the cover serve tomaintain the cover, grounding plate and base all in proper' angular relationship and if any great rotational torque is applied tothe cover or to the terminals 29 and 26a, when the control is mounted on a panel or support with the locating ears 65 engaging holes in the support, no shifting of the parts relative to each other will be possible. A shift of the ground plate could occur in other similar devices or might occur here if ears 6| were not in engagement with lobe 24h and as a consequence of this shift one of the'terminals of the resistance element might be grounded accidentally with disastrous results.

The variable resistance unit A is then assemv against the surface of ythe grounding plate of the next adjacent unit, thereby greatly increasing the rigidity of the assembled device and thecompactness thereof,- and permits integrallyformed portions of the grounding plate and end wall of the adjacent housing to be used as means for securing the units to each other in a most expedient and economical manner.

It will be quite apparent that the above described manner of constructing and connecting the variable resistance units to each other will often result in mis-alinement of the shafts of adjacent variable resistance units. Figs. 6 and 7 illustrate in a somewhat exaggerated manner the adaptability of the novel coupling means to shafts which are not in alinement with each other. The reduced portion 41h of the coupling member 41 prevents contact of the latter with the corners of the slots, and even though the member 41 is positioned at an angle to the respective shafts, a free, smooth drive therebetween is obtained. As will be noted in Fig. 7, the coupling members are provided with concave ends 41a to prevent contact with the journal bearing sections of the housing 3| or grounding plate 4|. It is therefore obvious that a universal coupling eil'ect is obtained between cooperating shafts, and a plurality of variable resistance units may be smoothly operated by a single actuating means despite material mis-alinement of shafts and rigid connections between the units. Nevertheless, the rotational play between shafts is very slight and practically immaterial.

' It is obvious that the specific embodiment of the invention illustrated and specifically described may be varied in many details of its construction within wide limits without departing from the spirit of the invention, and it is to be understood that the invention in to be limited only Within the terms oi the appended claims.

l claim:

l. ln a tandem variable resistance device, a plurality of variable resistance units fastened to each other, each oi' said variable resistance units having a cup-shaped metallic housing, notches in the side Walls of said housings, base plates having lugs extending from the peripheral edge thereof and positioned in the open faces or said housings with said lugs arranged in said notches, metallic grounding plates overlying some of said base plates, substantially alined journal bearings formed within the contour of the housings from the end walls of said housings and the corre1 sponding grounding plates, and individual shafts mounted in said substantially alined journal bearings, said shafts coupled to each other for simul neous actuation thereof.

2. In a variable resistance device in cornhina I tion, a plurality oi variable resistance units con-s nected in tandem relationship, a cup-shaped housing for each of said units, an actuating shaft projecting from one of said units and stub shafts in the remainder of said units, a metallic grounding plate positioned in the open end ci the housings of said stub shaft units, said shafts being Within the contour of the units and supported at opposite ends on the shell and grounding plate, ears on said housing bent over into engagement with said grounding plates, oilset portions in the end wall of said housings to provide clearance for the said ears of the next adjacent housing, cooperating means on said grounding plates and next adjacent housing end walls for securing said units to each other, and means for coupling said shafts for simultaneous operation thereof.

3. ln a variable resistance device in combination, a plurality of variable resistance units conaiaaeai nested with the bottom surface of one unit against the top surface of the nent adjacent unit, metallic housings surrounding said units, projecting portions on the bottoms of said units, oni-set portions in the top surface of the next adjacent unit interlocking with said projecting portions, individual shafts for said units, said shafts being within the contour of the units and supported at opposite ends on the end Walls of the units, and means for coupling said shafts ior simultaneous operation thereof.

4. ln a variable resistance device in combination, a plurality of variable resistance units cone nected intandem relationship, cup-shaped metallic housings surrounding said units, base plates covering the open ends of said housings, terminals secured to said base plates, a portion oi the end Wall of the cup-shaped housings adjacent to and overlying said terminals being off-set to provide clearance for the latter, individual shafts ings having apertures therein, said ears cooper ating with said apertures to secure said units to each other, alined shafts journalled between said metallic members and their corresponding housing end walls and within the contour of said units, notches in the ends of adjacent shafts, and a universal coupling member positioned in the notches oi each adjacent pair or" shaft ends.

RMWTN C. SCHELLENGER. 

